We propose to elucidate certain conformational aspects of gonadotropins (e.g., luteinizing hormone, chorionic gonadotropin, pregnant mare serum gonadotropin, and follicle-stimulating-hormone), growth hormone, prolactin, adrenocorticotropin, and placental lactogen. This will include measurements of circular dichroism, fluorescence, electron-spin-resonance, ultra-centrifugation, and viscosity. For the gonadotropins particular attention will be devoted to the nature of the conformational changes occuring upon subunit association-dissociation. For growth hormone the studies will be concerned mainly with membrane interactions as monitored by adiabatic rapid passage electron-spin- resonance. We propose to investigate the molecular mechanisms involved in the metabolism (i.e., plasma clearance, urinary excretion, tissue uptake, intracellular catabolism, and inactivation) of the various pituitary hormones. The data will be analyzed using a compartment model with an intravascular pool and several extravascular pools. Structure- function relationships of gonadotropins will be examined by determining the effects of specific amino-acid modifications on binding to Leydig cells and on the stimulation of steroidogenesis and cyclic-AMP in Leydig cells. The effects of chemical and enzymic modification of growth hormone will be investigated in an effort to define active-site peptides and residues essential for somatomedin induction. These studies are aimed at elucidating on a molecular level the relationships between hormone structure and function, biological actions, and metabolism.